Combined effects of occupational noise exposure and shiftwork on performance tasks in a seafaring population

This study was undertaken to complement a cross-sectional survey of the combined effects of selfreported workplace stressors. Data were collected from seafarers on board support vessels for the North Sea oilrigs as part of a project on offshore fatigue. These data could also be used specifically to address whether there were any cognitive effects associated with working in loud noise at night that were different to working in loud noise during the day, low noise at night or low noise during the day. The participants were 62 male workers from 3 different vessels. Their mean age was 40.3 years. Individuals were from a range of different jobs onboard the vessels. There were two between-subjects factors (day/night shift and noise exposure) and one within-subjects factor (test session). Workers were asked to complete a battery of computer tests both before (Pre-shift) and after (Post-shift) their shift on one day. Four tests were presented using laptop computers. These tests were visual analogue mood scales, a simple variable fore-period reaction time, and categoric search and focused attention choice reaction time tasks. The mood scales were presented at the beginning and end of the testing session. Occupational noise exposure (Leq) was measured over a two-day period using a dosimeter. Workers were categorised into day/night workers by their shift pattern. Regression analyses distinguishing noise exposure, day/night shift and their interaction were performed on the data from each test session and the change score between the start and end of the shift. Noise exposure was associated with increased alertness but also with slower reaction times. Those working night shifts showed a large drop in alertness over the course of work and became slower at tasks requiring more difficult responses. There were also a limited number of interactions between noise and shift, such as more lapses of attention (very long response times) but fewer incorrect responses in the noise/night-work condition. The findings suggest that these techniques may provide valuable information about the possible combined effects of occupational stressors in situ. The present analyses are based only on a small number of night workers and further consideration of effects of potential confounding influences must also be undertake

Combinations of workplace stressors and work related injuries

Consideration of factors associated with increased accident likelihood has tended to concentrate on the influence of one specific factor (for example, noise) and other influences are either not considered or are controlled for. The aim here was to examine the influence of combinations of stressors on the prevalence of workplace accidents using self-report measures of exposure, health and work outcomes. Logistic regression analyses were carried out, with 'work-related/non-work-related accident' as the dependent variable. The main predictors were combinations of physical agents (noise, fumes, hazardous substances) and temporal stressors (night and shift work, long working hours). Additional predictors - the job demand-control-support model (Karasek 1979; Johnson and Hall 1988) and home-work interface (HWI) were also investigated. Other measured predictors (i.e., age, sex and social class based on occupation) were included in all analyses. There was some evidence for an increased likelihood of work-related accidents in those exposed to combinations of stressors - increased likelihood was largely due to independent effects of stressors, particularly noise. Certain stressors were also associated with a decreased risk of having a work-related accident (i.e. unpredictable work hours). Job-demand-control-support did not have a major impact on predicting work-/nonwork-related accident likelihood. Prevalence of accidents at work largely reflected social class based on occupation - 'skilled manual workers' or 'partly skilled workers' were most likely to have an accident

Combined effects of occupational hazards: The impact of combined stressors on health and work performance

There exists a significant body of evidence regarding the effects of occupational hazards. These effects are often considered in isolation, yet a significant proportion of the workforce is exposed to several hazards at a time. The purpose of this study was to investigate the combined impact of workplace factors on mood, cognitive performance and physiology. Participants completed a battery of objective measures before and after work, as previous research (e.g. Broadbent et al. 1989) has shown the difference between before and after work measures to be a good indicator of workload demands during the day. The test battery was performed on the first and last days of the working week. Subjective information regarding chronic and acute (i.e. daily) exposure to hazards was also collected. Mean composite 'total negative factors' scores were created for exposure to chronic and acute stressors (e.g. noise, exposure to hazardous substances, job demand): median splits of these variables were then entered into a series of ANOVAs where mood, simple reaction time and physiology served as dependent measures. Findings indicate that chronic exposure to negative factors results in increased susceptibility to fatigue, over the course of the testing session, working day and working week

A greener approach to hydrometallurgy: highly selective separation of cobalt from nickel by solvent extraction with undiluted phosphonium ionic liquids

Lecture given by Sil Wellensstatus: publishe

An environmentally friendlier approach to hydrometallurgy: highly selective separation of cobalt from nickel by solvent extraction with undiluted phosphonium ionic liquids

A green solvent extraction process for the separation of cobalt from nickel, magnesium and calcium in chloride medium was developed, using undiluted phosphonium-based ionic liquids as extractants. Cobalt was extracted to the ionic liquid phase as the tetrachlorocobaltate(II) complex, leaving behind nickel, magnesium and calcium in the aqueous phase. Manganese is interfering in the separation process. The main advantage of this ionic liquid extraction process is that no organic diluents have to be added to the organic phase, so that the use of volatile organic compounds can be avoided. Separation factors higher than 50 000 were observed for the cobalt/nickel separation from 8 M HCl solution. After extraction, cobalt can easily be stripped using water and the ionic liquid can be reused as extractant, so that a continuous extraction process is possible. Up to 35 g L-1 of cobalt can be extracted to the ionic liquid phase, while still having a distribution coefficient higher than 100. Instead of hydrochloric acid, sodium chloride can be used as a chloride source. The extraction process has been upscaled to batch processes using 250 mL of ionic liquid. Tri(hexyl) tetradecylphosphonium chloride, tri(butyl)tetradecylphosphonium chloride, tetra( octyl) phosphonium bromide, tri( hexyl) tetradecylphosphonium bromide and Aliquat 336 have been tested for their performance to extract cobalt from an aqueous chloride phase to an ionic liquid phase. Tri( hexyl) tetradecylphosphonium chloride (Cyphos IL 101) turned out to be the best option as the ionic liquid phase, compromising between commercial availability, separation characteristics and easiness to handle the ionic liquid.status: publishe

Quantification of the solubility of metal salts in ionic liquids

Although ionic liquids are being considered as super solvents for many classes of compounds, the solubility of metal salts very strongly depends on the anion. Whereas metal salts can be very soluble in ionic liquids with coordinating anions (e.g. chloride, acetate or thiocyanate ions), it is very difficult to dissolve them in ionic liquids with weakly coordination anions, such as bis(trifluoromethylsulfonyl)imide ionic liquids. So far, only limited quantitative data have been reported on the solubility of metal salts in ionic liquids. We have started a research program to determine the solubility of different salts of main group elements and transition metals in ionic liquids, with an emphasis on chloride salts. Total-reflection X-ray fluorescence (TXRF) has been used as the analytical method of choice for monitoring the metal ion concentration in ionic liquids and for the determination of halide impurities in the ionic liquid solvents. This technique allows to work with small sample sizes and requires a minimum of sample preparation and calibration. Speciation of dissolved transition complexes has been done mainly by UV/VIS absorption spectroscopy. A major outcome of our work is that the intrinsic solubility of metal chlorides in bis(trifluoromethylsulfonyl)imide ionic liquids is very low. Any observed solubility can be attributed to impurities of halides and water in these ionic liquids. A linear relationship was found between the concentration of chloride impurities and the solubility of cobalt(II) chloride. The solubility of metals salts in ionic liquids with coordinating anions is very high, due to the formation of anionic metallate complexes. These results are of importance for the use of ionic liquids in hydrometallurgical or solvometallurgical processes.Poster presented by Sil Wellensstatus: publishe

Separation of cobalt and nickel by solvent extraction with two mutually immiscible ionic liquids

The proof-of-principle for the separation of metals by solvent extraction using two mutually immiscible ionic liquids is given. Cobalt was extracted from the ionic liquid 1-ethyl-3-methylimidazolium chloride to the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate. A distribution ratio of 44 was obtained. Cobalt could be selectively separated from nickel, with a separation factor of 207. The extraction mechanism was elucidated using UV-VIS absorption measurements. The mutual solubility between the two ionic liquids was determined by 1H NMR. Processing steps such as washing, stripping and regeneration of the ionic liquid phases are discussed.status: publishe

Carbene formation upon reactive dissolution of metal oxides in imidazolium ionic liquids

Metal oxides were found to dissolve in different imidazolium ionic liquids with a hydrogen atom in the C2 position of the imidazolium ring, but not if a methyl substituent was present in the C2 position. The crystal structure of the product that crystallised from an ionic liquid containing dissolved silver(I) oxide showed that this was a silver(I) carbene complex. The presence of carbenes in solution was proven by 13C NMR spectroscopy and the reactions were also monitored by Raman spectroscopy. The dissolution of other metal oxides, namely copper(II) oxide, zinc(II) oxide and nickel(II) oxide, was also studied in imidazolium ionic liquids and it was found that stable zinc(II) carbenes were formed in solution, but these did not crystallise under the given experimental conditions. A crystalline nickel(II) carbene complex could be obtained from a solution of nickel(II) chloride dissolved in a mixture of 1-butyl-3-methylimidazolium and 1-ethyl-3-methylimidazolium acetate.status: publishe

A continuous ionic liquid extraction process for the separation of cobalt from nickel

A continuous ionic liquid extraction process using the ionic liquid trihexyl(tetradecyl)phosphonium chloride (Cyphos® IL 101) has been developed for the selective extraction of cobalt from nickel. The performance of this continuous extraction process is competitive with that of currently applied industrial processes. Moreover, the elimination of volatile odorous compounds from the extraction phase leads to environmentally friendlier and healthier working conditions.status: publishe